1. Field of the Invention
The present invention relates to a photolithography process, and more particularly, to a photoresist-coating apparatus and a photoresist-coating method using the same.
2. Discussion of the Related Art
With the rapid development of information technology, flat panel display (FPD) devices having advantages of thin thicknesses, light weights and low power consumption, have been developed and have replaced cathode ray tubes (CRTs). The FPD devices include liquid crystal display (LCD) devices, plasma display panels (PDPs), electroluminescent display (ELD) devices and field emission display (FED) devices.
An FPD device may be manufactured through a substrate-fabricating process for forming first and second substrates and a cell process for completing the FPD device by attaching two substrates with a phosphoric material layer or a polarizing material layer therebetween.
In general, to shorten processes and improve production yields, the substrate-fabricating process and the cell process may proceed over large-sized substrates, each of which may include a plurality of cells corresponding to respective display panels and may be referred to as a mother glass substrate.
According to this, in the substrate-fabricating process, thin film deposition, photolithography and etching steps may be repeatedly performed over first and second large-sized substrates to form elements such as pixels and thin film transistors in each cell area.
Meanwhile, in the cell process, seal patterns for attaching substrates may be formed on one of the first and second large-sized substrates, the first and second large-sized substrates may be attached with a polarization material layer, for example, therebetween, and the attached large-sized substrates may be cut by each cell to obtain a plurality of flat panel display devices.
Here, the photolithography step includes applying photoresist to a substrate which includes a thin film thereon, exposing the photoresist to light through a mask which includes predetermined patterns, and developing the light-exposed photoresist to thereby form photoresist patterns corresponding to the patterns of the mask.
At this time, to apply the photoresist to the substrate, a spin coating method or a slit coating method may be used. In the spin coating method, the photoresist may be dropped on the substrate, and then the substrate may be turned, so that the photoresist may be uniformly applied to the substrate. In the slit coating method, the photoresist may be applied to the substrate by scanning a nozzle which has a slit shape along a direction and discharging the photoresist through the nozzle.
The spin coating method has an advantage that the substrate can be uniformly coated with the photoresist. However, as the size of the substrate increases to provide a large-sized display device, the substrate gets large and heavy, and thus it is difficult to turn the substrate. Accordingly, recently, the slit coating method has been widely used.
FIG. 1 is a view of illustrating a slit coating apparatus according to the related art.
In FIG. 1, a substrate 2 to be processed is disposed on a stage 10, and a slit coating apparatus 20 for applying photoresist to the substrate 2 is disposed over the stage 10.
The slit coating apparatus 20 includes a storage unit 30, a supply channel 34 and a nozzle 36. The storage unit 30 stores and supplies photoresist. The supply channel 34 provides a path of the photoresist from the storage unit 30 to the nozzle 36. The nozzle 36 discharges the photoresist to the substrate 2 on the stage 10.
The nozzle 36 may be a slit nozzle having a bar shape across and over the substrate 10. The nozzle 36 scans and moves along a direction and discharges the photoresist on a substantially entire surface of the substrate 2, thereby coating the substrate 2 with the photoresist.
However, the related art slit coating apparatus 20 has several disadvantages.
More particularly, even though particles exist on the substrate 2, the related art slit coating apparatus 20 does not have any means settling the matter, and a photoresist layer may be non-uniformly formed. To solve the problem, the slit coating apparatus 20 may include a particle-detecting sensor (not shown), and the particles on the substrate 2 can be detected by the particle-detecting sensor. However, there frequently happens misoperation of the particle-detecting sensor.
As a first cause of the misoperation, the substrate 2, on which a photoresist layer is formed by the slit coating apparatus 20, may be a mother glass substrate and may be cut into a plurality of cell areas, each of which constitutes one display panel, in the following cutting step. The particle-detecting sensor may misoperate due to interference phenomenon from difference between layers in the cell areas and in regions between adjacent cell areas. That is, layers formed in each cell area differ from layers in the region between adjacent cell areas.
Second, to uniformly apply the photoresist to the substrate 2, the nozzle 36 may accelerate or decelerate at a specific area. At this time, even though there is no particle, the particles-detecting sensor may perceive that there exist particles due to acceleration or deceleration of the nozzle 36 and may misoperate.
When the particle-detecting sensor misoperates, an operator does not judge that the particle-detecting sensor misoperates but judges that there exist particles on the substrate 2. Accordingly, after stopping the slit coating process, the particles on the substrate 2 are checked. Therefore, the efficiency of the process is lowered.